Congestive heart failure (CHF) is a condition in which the heart is unable to pump enough blood to meet the metabolic needs of a patient's body. The condition results in the patient having shortness of breath, weakness and a lack of stamina, fatigue, exercise intolerance and fluid retention which results from an inadequate flow of blood to the patient's kidneys. CHF is a progressive disease that involves the continuing enlargement of the heart muscle in response to the low blood output (cardiac output). The harder the heart works to pump more blood, the more enlarged it becomes. The more enlarged the heart becomes, the more work the heart must do to pump the same amount of blood. The progressive cycle of the disease has few symptoms until the heart is unable to do more work. Often, by the time symptoms are noticed by the patient, the enlargement is pronounced and the heart is unable to provide enough cardiac output to support normal lifestyle activity. Drug treatments that attempt to increase cardiac output tend to facilitate the progression of the disease. Conversely, drug treatments that lower cardiac output tend to slow the progression of the disease. However, this can severely limit the patients lifestyle, leaving many patients effectively immobile or worse. Many CHF patients require extensive and expensive treatments both on an in-patient and out-patient basis.
CHF affects well over three million people in the United states alone. Moreover, there are over 400,000 new cases of CHF diagnosed every year.
The enlarged hearts of many CHF patients do not contract in the normal manner in that the right and left ventricles of the heart do not contract at the same time. This lack of synchronicity causes the heart to pump less blood than it would if they were to contract together. Conventional pacing of the right ventricle (RV) or right atrium (RA) has not been found to be effective in causing the left ventricle (LV) to contract at the same time as the RV in most CHF patients. In many CHF patients, the natural conductance of the heart between the RA, RV and the LV has been compromised.
Others have attempted to treat CHF by placing pacing leads in the right heart (RA and/or RV) and on the outside of the LV. These pacing leads are connected to a power source that supplies electrical signals to the right heart and to the LV to cause them to contract in the normal manner. This has been found to be effective in controlling cardiac contractions. However, placing the pacing lead on the outside of the LV requires a surgical procedure which is both expensive and risky, especially given the weakened condition of CHF patients.
The present assignee, Guidant Corporation, has recently introduced a treatment for CHF wherein a pacer lead for the LV is advanced through the ostium or opening of the coronary sinus (located in the RA) and into the venous drainage system of the LV which drains into the coronary sinus. This allows the RA and/or RV and LV pacer lead placement for CHF treatment utilizing the less invasive and less risky percutaneous catheterization procedures used to position the RA and/or RV lead(s) in conventional pacing. Thus many more CHF patients with conduction abnormalities can be treated. This procedure has been found to greatly enhance the heart's pumping efficiency and to increase the patient's cardiac output to the extent that the patient can frequently resume normal daily activity and/or benefit from drug therapy.
To access the coronary sinus through the ostium thereof, typically a guiding catheter with a shaped distal extremity is introduced into a vein in the patient's chest using a percutaneous catheterization procedure. The guiding catheter is advanced through the patient's vasculature until its distal end is within the patient's RA via the superior vena cava. Approaches via the superior vena cava are preferred over via the inferior vena cava for two reasons. The chest area is used for implanting the power source and is, therefore, already prepped and easily accessible. The inferior vena cava approach involves cannulating the femoral vein, which is more prone to infection and requires longer and, therefore, more difficult to control devices. To seat the distal end of the guiding catheter in the coronary sinus ostium, the proximal end of the guiding catheter which extends outside of the patient is torqued to rotate the shaped distal end while further advancing the catheter so as to guide the distal tip of the guiding catheter into the ostium of the patient's coronary sinus.
The ostium of the coronary sinus, which drains the venous blood from the heart muscle into the RA, is in varying positions, guarded by valve-like flaps of varying shape and resides in an RA of varying shape. The ostium is generally located between the tricuspid valve and the inferior vena cava, near the inferior base of the RA. Additionally, the path of the coronary sinus just distal to its ostium may take off from the ostium in various curves or angles. These variations are especially pronounced from CHF patient to CHF patient. Therefore, much time can be consumed attempting to place the distal tip of the guiding catheter into the ostium and to advance the distal tip an appropriate distance within the coronary sinus.
Once placed within the coronary sinus, the distal tip of the guiding catheter can be easily dislodged during the subsequent advancement of a guidewire into position within the vasculature of the coronary sinus which is employed to deliver the pacing lead into the coronary sinus. The tip may be easily dislodged, because it is unlikely that the shape of the distal portion of the guiding catheter will match the shape of the RA closely enough to provide good support (resist guiding catheter tip movement). Also the orientation of the distal tip of the guiding catheter may not match the take off curve or angle of the coronary sinus, causing any inserted devices to immediately contact the wall of the coronary sinus. Thus, as a guidewire is manipulated and advanced through the guiding catheter into the coronary sinus, the force that the guidewire applies to the wall of the guiding catheter may push the distal tip of the guiding catheters out of the ostium. This may result in a damaged guidewire and/or loss of access to the coronary sinus.
Once the guidewire is positioned well within the coronary sinus, the current procedure is to replace the guiding catheter with a special lead placement catheter. If, due to lack of guide support or the proper orientation of its tip, the guidewire is not deep enough into the coronary sinus, then the guiding catheter may pull the guidewire out of the coronary sinus as the guiding catheter is removed during the replacement procedure.
The coronary sinus, which drains the venous side of the patient's heart into the right atrium through the ostium, is at a difficult position, so much time can be taken merely to place the distal tip of the catheter within the ostium. Passing a pacing lead through the lumen of the guiding catheter can displace the guiding catheter, requiring the replacement thereof into the coronary sinus ostium.
It has been found that the procedure of accessing the coronary sinus of a patient's heart having CHF, is very time consuming. The hearts of CHF patients are deformed, so that finding the coronary sinus ostium is difficult. The existing guiding catheters used for other purposes have been found to be very ineffective in both finding the coronary sinus ostium and once found, maintaining access with the coronary sinus during the procedure.
The present invention satisfies these and other needs.